Avi has dysgraphia, a handicap that affects his writing: He transposes words and letters. His manuscripts are often covered with red marks that indicate corrections in syntax and spelling. When his dysgraphia was diagnosed, he was told that he would never become a writer, but Avi had always been an avid reader, and in spite of once flunking out of school because of his bad writing, he strived to become a writer. In the meantime, he took up another seemingly unlikely career, that of librarian.

After earning Bachelor's and Master's degrees in 1959 and 1962 from the University of Wisconsin, he earned a Master's in Library Science from Columbia University.

He worked as a librarian in the Performing Arts Research Center at the New York Public Library from 1962-70, then as an assistant professor and librarian at Trenton State College (New Jersey) from 1970-86.